European Patent No. 0 221 287 B1 described a sunshine roof panel for a car in which solar cells are embedded in a resilient plastics material beneath a pane of glass. The sunshine roof has a curvature adapted to the aerodynamic shape of the vehicle, but the design of the edge region of the unit which integrates the solar generator into the sunshine roof construction is not described.
It is also known from German Patent Application No. 37 37 183 A1 to provide a solar generator for use in a sunshine roof of a car with a plastic frame produced by the RIM process (reaction injection molding process), a multi-component polyurethane elastomer being used as plastics material. In this arrangement, however, the solar cells are covered on both sides by a rigid panel, namely by a pane of glass at the top and by a pane of glass or a metal sheet at the bottom, so that the resulting roof panel becomes quite thick and heavy. These drawbacks must be allowed for when designing the actuating elements for the roof panel.
The same applies to a transparent sunshine roof panel with a solar unit described in German Patent No. 41 05 389 C1, in which the surface region located in the outer edge region of a transparent sheet is lined with more powerful, but non-transparent crystalline solar cells and, in a different surface region, with less powerful but transparent amorphous solar cells. This solar unit composed of various solar cells is enclosed between two panes of glass of which the outer edges are surrounded by a frame which can be formed as a polyurethane foam surround.
With known roof panels which are designed as solar generators and are already fitted in mass-produced cars such as the Audi A6 and A8, the internal surface of the roof panel, which is surrounded by a foamed plastic frame, accommodates crystalline solar cells. However, as the plastic frame has relatively wide frame parts, for reasons of strength and also to accommodate reinforcing profiles which may be required in the frame, only the internal framed region of the roof panel is available for accommodating crystalline solar cells, limiting the attainable utilization of solar energy.
The Applicant's attempts to accommodate crystalline solar cells in a generic solar generator, i.e. using a lightweight solar generator with a covering film on the underside, in the frame region and to incorporate them during foaming in order to achieve better use of solar energy have hitherto failed. The solar cells had a very high breakage rate during the foaming process.